Nucleus, Edinger-Westphal

Opioids elicit pupiiiary narrowing (miosis) by stimulating the parasympathetic portion (Edinger-Westphal nucleus) of the oculomotor nucleus. 

Weninger SC, Peters LL, Majzoub JA (2000) Urocortin expression in the Edinger-Westphal nucleus is upregulated by stress and corticotropin-releasing hormone deficiency. Endocrinology 256-263... 

Yamamoto H, Maeda T, Fujimura M, Fujimiya M (1998) Urocortin-like immunoreactivity in the substantia nigra, ventral tegmental area and Edinger-Westphal nucleus of rat. Neurosci Lett 243 21-24... 

Miosis, or the pinpoint pupillary response to the opioids, is diagnostic of the use and abuse of the opioids. No tolerance to such an effect is observed. Miosis is due to disinhibition of the Edinger-Westphal nucleus in the cortex resulting in increased pupillary constrictor tone. 

Central nervous system depression is the usual effect of morphine, and sedation and drowsiness are frequently observed with therapeutic doses. When given in the absence of pain morphine may sometimes produce dysphora—an unpleasant sensation of fear and anxiety. The most important stimulatory effects of morphine in man are emesis and miosis. Miosis, due to stimulation of the Edinger-Westphal nucleus of the third nerve, occurs with all opioids. The combination of pinpoint pupils, coma, and respiratory depression are classical signs of morphine overdosage. Stimulation of the solitary nuclei may also be responsible for depression of the cough reflex (antitussive effect). Pharmacokinetics and metabolism... 

Fig. 5. The plate illustrates the ventral midbrain tegmentum as illustrated in the atlas of the rat brain of Swanson (1992), at levels approximately equivalent to those shown in Fig. 4. B and D are images of Nissl-stained sections. Abbreviations CLI, central linear nucleus of the raphe cpd, cerebral peduncle DGlb, dentate gyrus, lateral blade EW, Edinger-Westphal nucleus fr, fasciculus retroflexus hf, hippocampal fixure IF, interfascicular...

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